Multiple jet blasting charge



1mm 2K 195% a. s. BYERS MULTIPLE JET smsmxc camera Filed Feb. 16,

INVENTOR Patented June 27, 195% I 2,513,233 MULTIPLE our presume cannon,

Laud s. Byers, camel, .caiu.

Application February 16, 1950, Serial No. 144,478

1 Claim. (Cl. 102-24) principal purpose of providing a multiple jet efface of the charge adjacent to the surface-to be blasted or punctured. While the technique of using this principle has been vastly improved since the early discovery by Prof. Munro, maximum results have always required a more or less critical stand-off" distance between the face containing the cavity and the surface to. be blasted. While a marked increase in the perforating power of the blast was achieved through simple use of a cavity, proper stand-oil?" or spacing, as in the "bazooka has been found to be almost absolutely essential.

The theory underlying the cavity efliect is elusive in nature and is believed to still be awaiting a full and complete explanation.v It is known, however, that the action of the cavity is to concentrate the forceof the blast, and hence to localize its effect. It isxalso known that where the cavity is lined with a layer of. metal the ex-' plosion acts to transmit jets of molten metal together with jets of gas from the explosion of the charge. subjected to, both jets of metal and gas.

In seeking to increase the disrupting power of charges in blasting rock masses and in breaking up masses of metal, I have sought to still further augment this effect and to economize in the use of explosive as well as to avoid the calculations necessary to achieve the full benefits of the stand-off principle. In the course of experimentation, I have discerned that the penetrating, disruptive and splitting effect can be remarkably increased by use of a cavity employing a plurality, of concentric conical surfaces of revolution serving for jet deflection.

With this arrangement a succession of jets appear to strike the object to be blasted at spaced time intervals and in any event 'a. greatly augmented effect is produced. The effect is, then, not only'to penetrate deeper, than before, but also to split and tear apart, with greatly magnified results. Instead of a scattering effect, which is common with explosives, the effect is to break up and shatter the rock, ore or burden being blasted, and to drop the pieces substantially in situ.

The objects sought to be achieved by practice of the present invention are numerous. Among them is provision of a structure capable of producing either a radial splitting effect, or a linear splitting effect by utilizing the cavity effect in the form of either a concentrated or a linear charge. The invention also is directed to the Thus the object to be blasted is.

fact in which no stand-off" measurements are required, so that the base of the charge may under all conditions be in direct contact with the surface to be blasted. Furthermore. the invention contemplatesthe achievement of a blasting effect far out'of proportion to those achieved heretofore, by focusing thevarious jets which are transmittedby. the explosion of the charge,

whereby a disrupting effect far out of proportion to the amount of charge used can be attained. The invention further contemplates a multiple. jet effect which can be modified'to meet numerous 1 and varied conditions such as a long linear cut, a concentrated drilling effect, a localized shat-. tering or a circumferential cutting eiIect depending upon the shape, size and location of the object to be blasted.

The invention is'capable of application horizontal, vertical or inclined surfaces, and all such uses are contemplated. It is also concerned with a directing effect not only from" the cavity itself but also from the container, and with a guidin means carried by the charge container for insuring that the exploding cap will'have its effect directed ontothe rear of the cavity. Numerous other advantages will appear from the following description when it is read in connection with the accompanying drawings in which:

Figure l'is a central sectional view of a blasting charge of circular form having a multiple jet cavity in itslower or active face;

Figure 2 is a plan view of the charge shown in Fig. 1;

Figure 3 is an enlarged diagram showing the details of a preferred form of cavity embodying the multiple jet principle;

Figure 4 is a perspective view showing one form of explosive holding container adapted for use in applying the principle of the present invention to linear cutting operations;

Figure 5 is a sectional view of the container of Fig. 4 when filled with explosive;

Figure 6 is a sectional view showing the principle of the invention applied to the cutting of a cylindrical object; and

Figure 7 is a side elevation of a preferred form of the invention, parts being broken away to show the interior construction.

-as well as protect the explosive material from moisture and deterioration. The bottom or active face 6 of the casing contains a cavity designed to produce a plurality of downwardly converging jets which are produced by the com- 3 bination of conical surfaces of revolution designated A and B in Fig. 3. The cavity as shown is made up of two downwardly diverging concentric conical surfaces of revolution. The top or apex surface A is a complete cone, the sidewalls 98 and 8-1 of which are disposed at an angle of substantially 30 with respect to the base 6. The other conical surface B is a frustum of a cone, the sidewalls of which connect the bottom of the apex cone to the base and make an angle of substantially 60 with said base. In other words the surfaces joining the lines represented by I and 9 to the base 6 form an angle of substantially 60 with that base.

The cavity is centrally located in said base and of such a diameter compared with that of said base. as to form a fiat annular surface for engaging the surface to be blasted. The diameter of the cavity as shown is approximately one-third of the diameter of the coplanar base. The container 6 is completely closed and in manufacture may well include a cap or lid II which is secured in place after the container is filled. The reference character 12 designates a blasting cap guide which is disposed so as to position the inner end of the cap in direct line with the cavity underneath, and in such proximity to the cavity as to attain maximum results. This guide, which is concentric with the conical surfaces of revolution. may be of material such as that used in the container, and may be either integral with or separate from it.

As indicated above, it will be clear that when the charge explodes there is a greatly amplified effect due to the presence of the cavity in accordance with known principles. If the cavity is of symmetrical form or so designed that it contains but a single reflection point, the disrupting effect of the blast is greatly amplified over what it would be without the cavity, but its maximum effect can only be achieved by spacing the charge from the surface to be blasted. In other words stand-oil is required.

I have discovered, unexpectedly, that this effect may be greatly amplified by providing the cavity with a plurality of reflecting areas. When the charge is exploded, jets of gas are directed into intersecting relation, and produce extreme turbulence and disrupting action far in excess of the effect to be expected by the amount of explosive used. While it has been indicated in the literature that cavities embodying the Munro effect may have different shapes,.and even have more than one reflecting area, there has been no indication that an arrangment of the jets as here utilized will produce an unexpected result. There has also been no recognition of the fact that an arrangement such as disclosed herein will give unexpected results or eliminate the use of stand-off. Regardless of the explanation which underlies this principle, the fact remains that the amount of explosive required to produce a given disruptive and splitting effect may be materially reduced by arranging the jets as set forth herein, and this unexpected result would not be achieved by use of prior art structures.

The structure shown in Figs. 1 and2 is suitable for commercial blasting operations where large rock or metal masses are to be broken, and particularly in secondary shooting such as in quarries. The charge may be placed on a flat or inclined surface with the cavity in proximity to that surface, or it may be suspended beside a vertical or steeply inclined surface with the cavity adjacent to that surface.

As indicated above the principle embodying the present invention also has a wide application for lineal cutting, particularly for the cutting of metal, as in shipyards and commercial metal salvaging operations. In those operations. it is frequently necessary to make extended cuts in metal plates. Cutting torches are normally employed with great consumption of time and materials. I have found that the expense and time may be greatly reduced by use of the principles set forth herein, that is, by shaping the charge to provide the multiple jet scheme above described.

While the lineal cutting referred to above may be carried out in various ways, one practical scheme is that suggested by Figs. 4 and 5 of the drawing, in which there is shown a trough made of metal, treated paper, plastic or other similar material having upstanding sides l5 and I6 re versely bent to provide point contacts at I! and II with the surface to be blasted. The bottom of the trough is so formed as to provide three elongated reflecting areas I8, 20 and 2! of inverted V-shape and embodying the plurality of jets as described above. The trough will be placed in contact with the flat surface where a linear cut is to be made, and it will then be filled with some readily moldable explosive, indicated [4 in Fig. 5, such, for example, as blasting gelatin. Obviously other types of explosive material such as TNT, Amatol, RDX, or the like might be used. Where the linear cutting is to be applied to commercial operations it is preferred to use some high velocity material such as blasting gelatin which is a noncritical material readily available for industrial usage. When the trough is in contact with the surface to be blasted or cut, and the trough has been filled with explosive. it is exploded by means of a blasting cap or the like placed in the manner suggested in connection with Fig. 1. By the use of a small amount of explosive, a continuous linear cut is produced and its width will depend upon the spacing of the apices i! and I8. Obviously the wider the spacing the wider the cut and vice versa. The angles between the portions joining the points 19, 20 and 2| may be varied within wide limits, but it is generally a fact that the smaller the angle the more concentrated the blast, and conversely, the greater the angle the more the distribution of the blast.

It has been indicated above that the practice of the invention is by no means limited to the cutting of linear channels or shattering operations. Fig. 6 shows the application of the principle to the cutting of a cylindrical body such as a portion of a metal bomb casing, boilers, steel pipe, and the like, in which it is possible to place the charge entirely around the periphery of the object to be severed.

In Fig. 6 reference character 25 designates a cylindrical body of metal which it is desiredto sever without prolonged and expensive torch cutting operations. A plurality of the trough sections, shown in Fig. 4, are placed end-to-end around the periphery of the body 25 and are held together b means of a wire 26, the two ends of which are twisted together at 21 to hold the segments of the trough firmly against the body. Once placed, the segments are filled with blasting gelatin or other suitable explosive, as before. so that there is formed a continuous band of explosive material completely around the body. This material is then exploded by means of a booster charge or a blasting cap, to produce a cutting operation from all sides of the body effectively severing it with a single explosion.

Here, as in Fig. 4, it will be found that the width of the cut will depend upon the spacing of the apices' I1 and I8, and for practical operation it will, of course, be desirable to have the cut as narrow as possible in order to avoid wastage of material and to use the exposive power the most effectively.

It has been pointed out above how the peculiar fashioning of the cavity brings about unexpected results, and greatly reduces the amount of explosive required to perform a given task. This effect is even further accentuated through use of a preferred form of the invention as shown in Figure 7.

In Figure 7, 3| designates a base, preferably of metal, or molded or pressed pulp or plastic material, having a cavity constructed as in Figure 1. The top 32 of the container is dome-shaped and terminates in a flange 33 secured to base 3| as by a rolled bead 39. The top contains a guide tube 35 for a blasting cap as before, and the container is filled with explosive material as in Figure 1. As shown the base 3| is slightly thinner than top 32, as it has been found that use of a top thicker than the base enhances the effect. The important feature of this construction is the dome-shaped top which directs the explosive wave downwardly toward the object to be blasted, and produces an effect greater than is possible with the container of Figure 1.

While the exact theory underlying this behavior is not fully understood, it is believed that since the initiation of the detonation or explosive wave takes place at the top center of the dome, the wave has a greater tendency to be deflected downward in an umbrella action, thus greatly increasing the concentration of the shock on the object to be blasted; thereby enhancing the dis-' rupting' and splitting power of the charge, and assisting in the localized breaking eflfect which is so characteristic of the invention.

In utilizing the multiple de-phasing jet principle described herein it is desirable for cutting operations that a very fast explosive be employed. While the invention has been described as applied to only a few types of operation, it is to be understood that it is not limited to the particular types shown but is capable of wide application, not only commercially but for military uses as well. It might be pointed out that one of the outstanding advantages of the invention is the fact that it is extremely economical in use, a factor which is not ordinarily considered in warfare but becomes highly important in commercial operations. Forexample, in the breaking up of metal bodies, such as the heavy cast steel skulls which form in steel ladies, breaking of the material to form steel scrap has always been a major and diflicult problem. By practice of the present invention, utilizing a charge of the general character of that shown in Fig. 1, it is possible by the use of a relatively small amount of very fast explosive to quickly effectively and economically break up this skull where heretofore extensive mechanical and time consuming operations were required. The highly effective disrupting and splitting effect of the multiple jet is so pronounced that its application becomes possible to envirmonments where it has never before been found feasible to utilize explosives as a means of salvaging steel and other metal scrap. Since the characteristics of this arrangement are such that the broken pieces of the object being blasted 5 heretofore would have been impractical.

This application is a continuation-in-part of m application Serial No. 81,538 filed March 15, 1949.

Having thus described the invention, what is l claimed is:

A blasting unit for shattering rock masses with a minimum of lateral scattering, comprising a container made up of a coplanar circular base having a central inwardly deflected indentation l defining a cavity of approximately one-third of the diameter of said base and leaving a wide annular work-engaging surface, said cavity being formed with two concentric downwardly diverging conical surfaces of revolution, one comprising a complete cone forming the apex of the cavity and having side-walls disposed at an angle of substantially 30 degrees with respect to said base, and the other surface of revolution forming a frustom of a cone connecting the bottom of the apex cone with said base and having its side walls disposed at an angle of substantially 60 degrees with respect to said base, a shallow thick-walled dome-shaped top secured to said base and forming an umbrella-like blast deflecting surface embracing said indentation, an explosive charge filling said container, and a detonator in said top concentric with said conical surfaces of revolution.

LAUD S. BYERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 0 Number Name Date 1,440,601 Holran Jan. 2, 1923 1,534,011 Watson Apr. 14, 1925 1,810,000 Woodberry June 16, 1931 2,367,199 Church et a1. Jan. 16, 1945 2,371,151 Church et a1 Mar. 13, 1945 2,407,093 Mohaupt Sept. 3, 1946 2,409,848 Greulich Oct. 22, 1946 2,412,967 Church et a1. Dec. 24, 1946 2,415,814 Davis et a1 Feb. 18, 1947 FOREIGN PATENTS Number Country Date 579,279 Great Britain July 30, 1946 579,649 Great Britain Aug. 12, 1946 610,016 Great Britain Oct. 12, 1948 618,617 Great Britain Feb. 24, 1949 OTHER REFERENCES Zeitschrift fur das gensamte Schies and Sprengstofiwesen, May 15, 1914. pp- 183-187.

"Explosive with Lined Cavities," Birkhofl et al., Journal of Applied Physics, vol. 19, No. 6, pp. 563-582, June 1948.

Paper entitled The Hollow Charge Effect" by w. M. Evans, published March 9, 1950, by the Institution of Mining and Metallurgy.

Bureau of Mines, report #4371, Nov. 1948, part I, "Shaped Charge Applied to Mining."

"Studies of the Design of Shaped Explosive Charges and Their Effect in Breaking Concrete Blocks, Clark, 16 pp., AIME Technical Publication 2157, March 1947. Copy in Division 70. 

